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computational fluid dynamics

Forcing natural ventilation resources in a hybrid ventilated facility at KTH

In this paper a method to solve a design problem of hybrid ventilation system is proposedby building stack pressure around the ventilator using a flat bed, glass-shielded rectangular solarchannel. In support of this idea a CFD (Computational Fluid Dynamics) simulation based ontheoretical calculation is done. Here, natural convection and a k-e two-equation turbulence modelwere used together with the finite volume method.

Duct Airflow Measurement by Tracer Gas – Development of a New Portable Device for convenient HVAC Auditing

The development of a new device for the injection of tracer gas is discussed with the objective of practical application in the field of HVAC airflow measurements. The uniform tracer gas dispersion for very short distances, when measuring airflow by the constant emission method is of great interest. This new injection device has a compact tubular shape, with magnetic fixation to be easy to apply to duct walls. After a preliminary study with an initial prototype already tested, further detailed experiments had been carried out, culminating in a second prototype.

Complex Air Flow Behaviour in Complex Spaces - Design Optimization by CFD, Realization and Visualization

This paper shows the successful application of CFD simulations for analyzing complex room air flow problems in real applications and deriving optimized solutions.

CFD Modelling of Atrium-assisted Natural Ventilation

Using computational fluid dynamics (CFD) techniques to model buoyancy-driven airflows hasalways proved challenging. This work investigates CFD modelling of buoyancy-driven natural ventilation flows in a single-storey space connected to an atrium. The atrium is taller than the ventilated space and when warmed by internal heat gains producing a column of warm air in the atrium and connect space drives a ventilation flow. Results of CFD simulations are compared with predictions of an analytical model and small-scale experiments [1].

Numerical simulation of the flow field in the kitchen of a residential building with natural ventilation

The main goal of this work is the modeling of the flow field and temperature distribution in thekitchen of a house where natural ventilation techniques were implemented. The Fluent 6.1 commercial CFD software was used. The k- e turbulence model and the Boussinesq approximation for buoyancy were employed. The heat released from a water heater in continuous operation dictates the temperature distribution in the kitchen. Several simulations were performed by varying the boundary conditions and seeking agreement with the available experimental data.

Optimization of Hybrid Air-conditioning System with Natural Ventilation by Genetic Algorithm and Computational Fluid Dynamics

In order to clarify whether a combination of designs is optimal, design elements are divided intodesign variables and random variables in the inquiry process for the optimal design. Design variablesrelated to the model are selected by a genetic algorithm, and random variables related to outdoor condition are selected by the moment method. The whole process of optimization consisted of a two-step procedure to reduce the calculation loads for finding the optimal solution. This study carried out a simple analysis using a coarse mesh considering the calculation loads in the first step.

The Effect of Wall Porosity on the Flow Rate in a Building Ventilated by Cross Wind

Wind-driven cross-ventilation in a single-zone cubic building with two large openings is investigated using a computational fluid dynamics approach. We analyzed the driving force and the ventilation flow rate due to wind as a function of the relative location and geometry of the two ventilation openings. The aim is to understand how well the conventional simple macroscopic method predicts the ventilation flow rate and when the simple method fails. Parametric studies were completed using building envelope porosity as the primary variable of interest.

Single-sided natural ventilation through a velux roof window

This paper investigates the single-sided natural ventilation through a VELUX centre pivot roof window under natural weather conditions. The aim of the investigation is to develop an empirical formulation for air flow rate through a roof window based on CFD and tracer gas decay measurement methods. CFD can separate buoyancy and wind effects in the calculation of the air flow rate through a window opening, but it is difficult to isolate wind effect from buoyancy forces during measurements.

Determination of the Air Change Rate for Natural Ventilation with Regard to Energy Efficiency and Building Physics

The air exchange in a room with different windows and window geometries is investigated. The aim is to get reliable data for the air change rate and the air exchange efficiency for natural ventilation. Before using a CFD program for the calculations experimental studies have been carried out. In order to meet different demands we distinguish between short time and continuous ventilation. The results are availabe as figures, graphs or approximate equations.

Thermal effects on the dispersion of a gaseous contaminant in a naturally-ventilated room

The influence of thermal effects on the dispersion of a gas in a naturally-ventilated room is investigated using CFD in conjunction with measurements. The gas dispersion inside the room, with and without thermal effects, is characterised by a statistical analysis of the CFD-predicted gas concentrations at a large number of points across the room with a view to quantifying the thermal effects. It is concluded that even small temperature differences can lead to significantly different cross flow behaviour and rates of gas concentration decay at the relatively low air change rate considered.